Screen changer for hammer mills



R. J. REESE ETAL SCREEN CHANGER FORHAMMER MILLS Feb: 18, 195s- 3 Sheets-Sheet 1 Filed Jan. 23, 1956 VINVENTORJ Ppgzskrl P5551. and

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Feb. 18, 1 958 R. J. REESE ETAL SCREEN CHANGER FDR HAMMER MILLS 3 Sheets-Sheet 2 INVENTORS fli'f'flP/VIE'YS.

Feb. 18, 1958 R. J. REESE ErAL 2,823,869

SCREEN CHANGER FOR HAMMER MILLS Filed Jan. 25, 1956 5 Sheets-Sheet a 4+.+++++++++ u +++4+++4+ 4 4 4 4 +++++4++++ 4 O 4 L ++++++++++o 0+++++++++ +++++++++.++O +++++++i+ ++++++++++O G+++++4+++ +++++++++++OO++ T++++++ +0 0 .+++++i o0nv+++++++++ +00 0+++++++++ United States Patent SCREEN CHANGER FOR HAMMERZMILLS Robert JrReese, Carmel, and FI'E'IPH. Bailey, Indianapolis, Ind.

ApplicationJanuary 23,.19'56, Serial'.No. 560,674- 14 Glaims. (Gl.'-24-1-89) invention relates to a ha'mmer :mill, and more particularly Y to a remotely controlled screen changer for a hammer mill.

:It is an-object of the invention'to' provide a hammer "miIl -an'd a screen changer for-said mill, whereinys'aid -screen changer has a plurality of screens withwarying mesh sizes which. are insertable in and'withdrawable 'from the-mill. It is anotherobject of the invention toprovide an inexpensive screen changer for' hammer-=mills-ofsimpie construction which is operable for-theremote controlledEh-angingdf screens in'a hammermilliinua minimum len'gth of'time.

In-accordanee with the invention there'is provided a hammer-mill 'of the conventional type usuallyhavingan -auxiliarygrinding unitand a main grinder including a plurality ofrapidly rotatinghammers for grinding and crushing material fedinto said millagainstyan arcuate screen extending partially"around thecircumference of the='rotational-'path ofzthe harnmers. Atopcover on the "housing enelosing the mill is retractable "from its nor- 'mally" closed position i by means o'fa remotely controlled toggle lever -arnifrigidly attachedto saidtop cover to =aiford an openingin "the mill housing through which screens ot'varying mesh sizes may be interchanged in the *main g'riniier. The cover= section I is-'pivotallyconnected to curved rigid -*screen-loc'king straps within the mill housing that secure the "screen in a fixed' operating positi'oniaga'i'nst a pair of screen-supporting straps when said cover is lockedin place "onfthe millhousing.

There is further provideda screen' changing mechanism above the mill adapted to 1 hold a-plurality Tot grinding ""screensflusually of diiferent'meshsiZeQ The-screen fchang *er is comprised of a chain drivenrotatable drum which "carries said screens equidistantly spaced within the drum wa'l'lsf towardj'the :outer' rim of said drum. The screens jare"p ivotafll y*secured to the drum and areheld in a storagegposition through most of the rotation ofthe drum byisuitablegsupporting, means. The screen changer is rem 'tely contrdlledfor' the insertion =and extraction of "screens 'intojarid out of theJmilLthrough .the opening mtoyid 'd n' e' o o h mill ho s n The accompanying drawings illustrate ithe invention, In the drawings:

"Fig. 1 1 is, an end elevation of, a hammer riiilLWith a screen changer attached thereto; A .Eig. is. avertical. sectiontakenalong the line 2-2 of Fig 1 I .-3is an venlargedifragmentary view ofahammer mill, showingsint detail theremovable top cover, and,the

enumerating relationship between the-milland; the screen :-change r; associated-therewith; and

invention; thematerial 'to be; ground enters the hammer J millttthrou'gh .iasz'duct F and is, partially ground by. the filltfiliary 'grinder l2 comprisedaof: a rotor lltandza grind- 2,823,869 Patented Feb. 18, 1958 ice :through -an;i 1iletport"26; The main'grinderfl l is enclosediby a'housing zs havingvertical sidewalls 28 and 30 and amend Wall '32. All ofthe housing walls are unite'clfin a mannerto form 'dust tight joints for *encasing the main grinding "unit.

A drive shaft: 34 ,forthe-mill-z ttjournalled on -bearings '35"'ancl 36 is connected ,to *ahighspeed rnotor ii'l. The drive shaft fi' l turns a'rotor -38-having a plurality of radially extending hammers 40 'attached to said --rotor. The. rotor 38"revolveswithin an 'arcuateinner-mill casing 42 partially circumsrctibing the path followed by the 20 fhammers 40. A pair 'of arcuate-metal straps 46' of a lesser radius-thanthe inner millcasing 42 butt-against and are tightly -secured*to theginner face-of said casing 'alongfits lateral :edges forming a seat to support an armate screen '48}insertablein"the-mill-housing. The screen 4 8"when'locked in operating position is snbstantiallycoextensive with ,th'e;a r'cuate length of "the straps 46 :and forms a grinding surface operatively disposed from the ,grindingfa'ce'stlofthehammers 40; The material comminuted through "the screen 48 "clrops to the bottom of the n1ill1housing25 'where it, is picked; up and; carried by air currents created' by the "suction fan 152. The :ground material is lthenconductedby said: air currents {through an'exhaust duct 54'to a desired storage-area.

The outer millhous ing 25 isprovide'd with a removable cover 56' alongthe top of said housing immediately 'wi'thinthe side" walls 28'and"30.' "Thelo wer end ofthe cover 56is pivotally connected, as :at'"58,,"to'apivotal cover section 60 which overlapsthat section of-the mill housing adjacentssai'd removable coventhereby providing afdust-tight .seal' between the stationary and-movable components of the mill housing when the, cover is'locked in aclosetiposition. The remoyable;coverj56"is pivotally connectedby a pin62 'to a-pairofarcuate metalfstraps '64 circumscribing the screen; along its 11 lateral :edges and fixedly :securing said screen in 'an operative position againstthe screen supporting straps 46. -'l.he'loweryends of the straps64are pivotcd about-the inner mill casing 42 by a pin"66 so that when the :coverSfiis-removed the straps 64 will movetoward the mill -end'wall"32 away from the 4 screen unlocking it from an operative positionto permit saidscreen to he-extracted P from the mill.

'The cover "56 is rigidlyattached to a 'con'nectin'g arm 68 which is *pivotally-connected, 'asat70, to a-toggle lever-arm 72; V 'A-"resis'ting-stop arm "73 mounted on'said toggle "arm isengageable with a lug-75 mounted=0n a -floor above the-mill. A-lug76 on the: end-"wall 321 of the-mill housing is provided with a. pivotal joint; as at 78, for a lever arm 80 which is attached to the: pivotal cover section-60. Whenithe cover'56 .is removedwfrom the mill by 1 moving ilihfi toggle zlever arm 72 upwardly and outwardly; theilever iarm :guides the; pivotal;;sec-

tion 60.upwardly tosswing said section and;the-,coyer clear of the-,millnhousing,thereby providingan- Opening for changing screens insaid mill.

As ,shown in .Fig. 2 the screen 3 changer 82 ,isicomprised of a drum 84 having side,walls .,85 .and- 87 gud is rotatable about a horizontally disposed shaft 86 mounted on a mill frame member 88. A driven sprocket 90 on the shaft 86 is driven by a continuous chain 92 extending over a driving sprocket 94 mounted on a suitable support 95 at any desirable remote control point. The driving sprocket 94 is rotated by a crank 96 on said sprocket which is fitted with a'handle 98; said drive mechanism is adapted to rotate the drum 84 and is normally used to drive the drum unidirectionally in the direction of arrow shown in Fig. 2.

Three arcuate screens 48 are equidistantly spaced around the circumference of the drum 84 between the vertical side walls 85 and 87 with the open end of their arcs facing away from the drum shaft 86. Each screen is connected to a web 100 by means of hinges 102 fitted with suitable hinge pins 104. The opposite ends of the webs 100 are pivotally secured to the drum 84 by means of pins 106. A stop-lug 108 is positioned adjacent each pivotal connection 106 and substantially an equal distance from the circumferential rim of the drum 84 as the pivotal connections 106. When a screen is positioned toward the top of the drum 84, the web 100 rests on the stop-lug 108 holding the screen upwardly near the circumferential rim of said drum. As the drum is rotated, the screen at the top of the drum moves in a generally downward direction with the weight of the screen pulling the web 100 away from the stop 108. A guide rod 110 is laterally centered between the side walls 85 and 87 along the lower rim of the drum 84 adjacent the opening in the mill housing. Said guide provides a support for the free end of the screen 48 after it swings free of the stop-lug 108 and until it moves over the opening at the top of the mill housing formed by the removal of the top cover 56, from which point the screen drops into the mill and seats itself in an operative position. A similarly disposed guide rod 112 extends upwardly to the drum 84 from the opposite side of the mill opening to guide the free end of an extracted screen into a storage position within said drum.

In operation, the material to be ground enters the mill through the duct and a gross reduction in particle size is made by the auxiliary grinder 12. The partially ground particles then pass down through the duct 22 to the inlet port 26 and into the main grinder 24. The particles are then ground by the rotating hammers 40 impelling said particles through'the screen 48, and the finely ground material is carried by air currents created by the fan 52 through the duct 54 to suitable storage bins.

To change screens in order to produce a different particle size of the ground material the following sequence of operation occurs. After the flow of material through the duct 10 is stopped by any suitable gate or valve arrangement, the shaft 74 is pulled upwardly causing the toggle lever arm to move outwardly away from the mill pulling the lever arm 68 upwardly and outwardly away from the mill carrying the rigidly attached removable cover 56 to a like position. The outward movement of the cover 56 causes the pivotal section 60 to ride upward ly, pivoting about the pin 58 and the arm 80 such that the entire cover section is removed from the mill into the dotted line position as shown in Fig. 3. By means of the pivotal connections 62 and 66 the screen-locking straps 64 are pulled away from the screen 48 and rest against the end wall 32 when the cover 56 is removed from the mill, thereby releasing said screen for extraction from the mill.

When the cover 56 is removed the screen 48 may be extracted from the mill by turning the crank 96 to rotate the drum 82 in a clockwise direction as shown by the arrow in Fig. 2. The rotation of the drum pulls the screen upwardly out of the mill with the lower end of the said 'screen riding along the guide means 112 until the screen is held within the drum by its web 100 resting against the stop-lug 108.

Concurrently with the extraction of one screen another screen is being carried by the drum downwardly into position for insertion into the mill. The weight of the screen causes it to clear its stop-lug such that the free end of the screen rests on the guide member 110. When the screen passes the end of the guide member it drops down into the mill with its lower end resting on the screensupporting straps 46, as shown in dotted lines in Fig. 2. With the drum in this position the several screens are disposed in an unbalanced relationship about the axis of the drum, tending to rotate it in a counter-clockwise direction (Fig. 2). The driving force on the chain drive 90- -94 is then released, or the crank 98 reversed, to permit the unbalance to rotate the drum counter-clockwise and lower the new screen into the mill. The lower end of the screen rides downwardly around the screen-supporting straps 46 until said screen is in an operative position with its lower end lying adjacent the lower end of said screen-supporting straps 46. The shaft 74 then is moved downwardly to pivot the removable cover 56 into a closed position on the top of the mill and bring the straps 64 against the screen to lock it in an operative position. The drive for the mill is left on during the screen changing operation so that all the operator need do to resume grinding operations is to open an inlet to permit material to enter the mill.

Every sequence of the previously described screen changing operation is controllable from a remote operating station. The operator is able to make all of the necessary screen changing adjustments from a floor above the mill where most of his work activities occur; thereby alleviating the time consuming necessity of going up and down stairs to make changes for varying the particle size of the material being ground.

We claim as our invention:

1. A hammer mill, comprising a grinding chamber, a rotor having a plurality of hammers attached thereto revolving in said chamber, an arcuate screen disposed along the circumferential path of said hammers, means on said grinding'chamber for releasably retaining a screen along said circumferential path, an inlet and outlet port communicating with said grinding chamber, a housing enclosing said mill, a removable top cover on said housing, and

' a rotatable screen-changing drum carrying a plurality of screens and cooperating with said mill for the selective insertion and extraction of screens into and out of said mill, and being adapted for the storage of unused screens.

2. A hammer mill, comprising a grinding chamber, a rotor having a plurality of hammers attached thereto revolving in said chamber, an arcuate screen disposed along the circumferential path of said hammers, an inlet and outlet port communicating with said grinding chamber, a housing enclosing said mill, a removable top cover on said housing pivotally connected to screen-securing straps, and a rotatable screen-changing drum carrying a plurality of screens and cooperating with said mill for the selective insertion and extraction of screens into and out of said mill, and being adapted for the storage of unused screens.

3. A hammer mill as set forth in claim 2 with the addition that said screen-securing straps are pivotally connected to said top cover and pivoted on said grinding chamber for locking and unlocking said screens in an operative position.

4. A hammer mill, comprising a grinding chamber, a rotor having a plurality of hammers attached thereto re- .volving in said chamber, an inlet and an outlet port comtraction of screens into and out of said mill, and being further adapted for the storage of unused screens, and means on said mill for releasably looking a screen therein.

5. A hammer mill as set forth in claim 4 with the addition that said lower section on the housing cover is connected to a pivotal lever arm to swing said section and the cover upwardly and outwardly away from said mill.

6. A hammer mill, comprising a grinding chamber, a rotor having a plurality of hammers attached thereto revolving in said chamber, an inlet and an outlet port communicating with said grinding chamber, a housing enclosing said mill, a removable top cover on said housing with a pivotal lower section forming a dust-tight seal between said cover and the mill housing, a toggle lever arm attached to said cover for opening and closing said cover, an arcuate screen disposed along the circumferential path of said hammers in the grinding chamber, said screen being one of a plurality of screens pivotally connected to a rotatable drum disposed above said mill, said drum being adapted for the selective insertion and extraction of screens into and out of said mill, and being further adapted for the storage of unused screens, and means on said mill for releasably locking a screen therein.

7. A hammer mill as set forth in claim 6 with the addition that said toggle lever arm is operable from a remote control point by means of an upwardly extending shaft attached to said toggle arm.

8. In combination with a hammer mill having a housing enclosing a main grinding unit, a rotatable screen-changing drum disposed above said mill, a plurality of screens adapted for use in said mill connected to said drum, means on said mill for releasably looking a screen therein, and guide means disposed between said drum and the mill for guiding said screens into and out of the mill.

9. In combination with a hammer mill having a housing enclosing a main grinding unit, a rotatable screenchanging drum disposed above said mill, a plurality of screens adapted for use in said mill pivotally connected to said drum, means on said mill for releasably locking a screen therein, and guide means disposed between said drum and the mill for guiding said screens into and out of the mill.

10. In combination with a hammer mill having a housing enclosing a main grinding unit, a rotatable screenchanging drum disposed above said mill, a plurality of screens adapted for use in said mill, said screens being pivotally connected to webs pivotally secured to said drum, means on said mill for releasably locking a screen therein, and guide means disposed between said drum and the mill for guiding said screens into and out of the mill.

11. In combination with a hammer mill having a hous ing enclosing a main grinding unit, a rotatable screenchanging drum disposed above said mill, a plurality of screens adapted for use in said mill, said screens being pivotally connected to webs secured to said drum, stoplugs on said drum engageable with said webs for supporting said screens in a storage position within the drum, guide means disposed between said drum and the mill for guiding said screens into and out of the mill, and means on said mill for releasably locking a screen therein.

12. In combination with a hammer mill having a housing enclosing a main grinding unit, a rotatable drum disposed above said mill, a drive operable from a remote control point for rotating said drum, a plurality of screens adapted for use in said mill, said screens being pivotally connected to webs secured to said drum, guide means disposed between said drum and the mill for guiding said screens into and out of the mill, and means on said mill for releasably locking a screen therein.

13. In combination with a hammer mill having a housing enclosing a main grinding unit, a drum disposed above said mill, a plurality of arcuate screens pivotally mounted to said drum adjacent its circumference and adapted to be selectively disposed in an operative position in said mill, said drum being rotatable for withdrawing the operatively-positioned screen from said mill and inserting another of said screens therein, and means on said mill for releasably locking a screen in operative position therein.

14. in combination with a hammer mill having a housing enclosing a main grinding unit, a drum disposed above said mill, a plurality of arcuate screens pivotally mounted to said drum adjacent its circumference and adapted to be selectively disposed in an operative position in said mill, drive means interconnected to said drum and adapted to unidirectionally rotate said drum to withdraw a screen from operative position in said mill and dispose another one of said screens in position for insertion into said mill upon reverse rotation of said drum, said drive-means being releasable to permit such reverse rotation, and means on said mill for releasably looking a screen in operative position therein.

References Cited in the file of this patent UNITED STATES PATENTS 2,076,297 Gray Apr. 6, 1937 2,227,090 Hughes Dec. 31, 1940 2,360,892 Rench et al. Oct. 24, 1944 2,669,396 Nickle Feb. 16, 1954 2,710,149 Bryant June 7, 1955 2,771,249 Schutte Nov. 20, 1956 

